Facing retirement of the Space Shuttle in 2010, NASA has made a second attempt to ensure that competitive commercial providers are available to transport US cargo and crew to the International Space Station.
The US space agency has selected Orbital Sciences to replace Rocketplane Kistler (RpK) as a contractor under its Commercial Orbital Transportation Services (COTS) programme to demonstrate the capability to carry cargo to the ISS.
In 2006, NASA selected Space Exploration Technologies and Rocketplane Kistler for the COTS demonstration programme, but RpK's contract was cancelled in 2007 when the company failed to raise the required commercial financing.
Whereas NASA's original COTS competition attracted bids from only smaller players - Andrews Space, SpaceDev, SpaceHab and Transformational Space, as well as SpaceX and RpK - this latest round drew offers from industry leaders including Alliant Techsystems/Lockheed Martin and Boeing.
Orbital, which withdrew its financial backing from RpK's COTS team in late 2006, will develop the Taurus II medium-lift launch vehicle and Cygnus autonomous cargo spacecraft. NASA will provide $170 million towards the $320 million cost of developing the system.
Orbital says its COTS demonstration mission is scheduled for the fourth quarter of 2010, from NASA's Wallops Island facility off the coast of Virginia. The company says it will be ready to conduct "several" operational COTS missions in 2011 and up to eight ISS cargo flights a year by 2012 and 2013.
Equipped with pressurised or unpressurised cargo modules, the Cygnus manoeuvring spacecraft will be capable of delivering up to 2,300kg (5,070lb) of cargo to the ISS and returning 1,200kg of cargo to Earth.